Top-line results from a Phase III study show that ABP 501 met its primary endpoint compared with Humira (adalimumab) in terms of ACR20 response rate (ie a 20% improvement in the condition) at 24 weeks. Safety and immunogenicity were also comparable to adalimumab and key secondary endpoints included ACR50, ACR70 and DAS 28-CRP (another common measure) were also met.

Humira, the world’s biggest-selling drug, is approved across a number of indications, including RA, plaque psoriasis, polyarticular juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, Crohn's disease and ulcerative colitis. Amgen’s drug has now succeeded in RA and psoriasis trials but will face a lot of competition in the Humira biosimilar market from the likes of Novartis unit Sandoz, Boehringer Ingelheim and Zydus Cadila.

Amgen has nine biosimilars in development and expects to launch five of them between 2017 and 2019.